我有以下使用sample的{{1}}代码需要很长时间才能处理（因为执行了很多次）：
sapply问题在于我必须从矩阵中的权重中提取，这取决于samples = sapply(rowIndices, function(idx){
sample(vectorToDrawFrom, 1, TRUE, weights[idx, ])
})
中的索引。
是否有人有更好的想法从矩阵的行中绘制？
可再现的例子：
rowIndices答案 0 :(得分：1)
所以这是一种加快代码速度的方法。有一点需要注意：采样值不会与rowIndices“匹配”，尽管以正确的顺序排列是很简单的。 2）您只存储最后一次迭代，但这可能只是因为这是一个最小的可重复示例......
基本上，您应该只需sample每rowIndices一次rowIndices，因为rowIndices <- sort(rowIndices) ##sort the row indices and then loop
for (i in 1:15){
samples = unlist(sapply(unique(rowIndices),
function(idx){
sample(vectorToDrawFrom, sum(rowIndices %in% idx),
TRUE, weights[idx, ])
}))
}
Unit: milliseconds
expr
min lq mean median uq max neval cld
newForLoop 263.5668 266.6329 292.8301 268.8920 275.3378 515.899 100 a
OriginalForLoop 698.2982 705.6911 792.2846 712.9985 887.9447 1263.779 100 b
的范围是1-99，这是99次调用而不是1000次，这提供了巨大的加速。
我们可以在开始之前对行索引进行排序
rowIndices维持原始向量排序的方法是保存索引或原始set.seed(8675309)
weights = matrix(c(1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0),
nrow = 5, ncol = 3, byrow = T)
rowIndices = c(2,1,2,4)
vectorToDrawFrom = runif(3, 0.0, 2.0)
set.seed(8675309)
##This is the origal code
sample2 = sapply(rowIndices, function(idx){
sample(vectorToDrawFrom, 1, TRUE, weights[idx, ])
})
rowIndx <- order(rowIndices) #get ordering index
rowIndices <- sort(rowIndices)
set.seed(8675309)
samples = unlist(sapply(unique(rowIndices), function(idx){
sample(vectorToDrawFrom, sum(rowIndices %in% idx), TRUE, weights[idx, ])
}))
samples = samples[order(rowIndx)]
all(samples == sample2)
#[1] TRUE
向量。然后对行索引进行排序并继续。
from asyncio import streams, transports, get_event_loop
class CustomTransport(transports.Transport):
def __init__(self, loop, protocol, *args, **kwargs):
self._loop = loop
self._protocol = protocol
def get_protocol(self):
return self._protocol
def set_protocol(self, protocol):
return self._protocol
# Implement read/write methods
# [...]
async def custom_create_connection(protocol_factory, *args, **kwargs):
loop = get_event_loop()
protocol = protocol_factory()
transport = CustomTransport(loop, protocol, *args, **kwargs)
return transport, protocol
async def custom_open_connection(*args, **kwargs):
reader = streams.StreamReader()
protocol = streams.StreamReaderProtocol(reader)
factory = lambda: protocol
transport, _ = await custom_create_connection(factory, *args, **kwargs)
writer = streams.StreamWriter(transport, protocol, reader)
return reader, writer